Question

Answer 1

Bài 4:
Do AC//BD(gt)
\(\Rightarrow\dfrac{OA}{AB}=\dfrac{OC}{CD}\)(Định lí Thalès)
\(\Rightarrow\dfrac{2}{3}=\dfrac{3}{CD}\)
\(\Rightarrow CD=\dfrac{3\cdot3}{2}=4,5cm\)
\(\rightarrow\)Chọn B
#kễnh

Answer 2

Câu 3:

CN/AN=2/5

=>\(\dfrac{CN}{CA}=\dfrac{2}{5+2}=\dfrac{2}{7}\)

Xét ΔCAB có NM//AB

nên \(\dfrac{CN}{CA}=\dfrac{CM}{CB}\)

=>\(\dfrac{CM}{CB}=\dfrac{2}{7}\)

=>BC=7/2CM

=>x=3,5

=>Chọn C